1. Field of the Invention
The present invention is directed, generally, to continuous metal casting, and more particularly to a method and apparatus for electrode or metal ingot casting.
2. Description of the Invention Background
Over the years, a variety of methods and improvements have been developed for casting metal electrodes and ingots. An electrode essentially comprises a solid cast metal block that is formed to be remelted and cast into an ingot, or into a certain geometric form. To accomplish the remelting of the electrode, an appropriate amount of electrical current is applied to the electrode utilizing known techniques and process controls. Thus, an electrode is essentially an intermediate product used in metal casting processes and an ingot is a finished product that is usually subsequently subject to mechanical deformation, such as forging or rolling.
Metal electrodes may be formed utilizing a variety of casting processes. For example, electrodes may be continuously casted in a vertically oriented process wherein the electrode is cast into a stationary mold from plasma arc, electron beam, vacuum induction, skull induction, skull or ac furnaces.
FIGS. 1-4 illustrate the conventional dovetail assembly and electrode forming process in vertical continuous casting. Conventional continuous casting of steel and titanium electrode melting in electron beam, plasma arc or skull furnaces typically uses a supporting mechanism, such as a cylindrical block 2, that is machined to include a dovetail 3. The cylindrical block 2 is detachably engaged to side wall 4 to form a vertical continuous casting vessel 5.
During vertical continuous casting, molten metal is introduced into, and fills, the vessel 5. Because the cylindrical block 2 is made from a conductive metal, the cylindrical block 2 conducts heat away from the molten mass, and thereby encourages solidification near the bottom of the vessel 5. As is common in continuous casting, the cylindrical block 2 is detached from the side wall 4 and is mechanically moved downward to grow the electrode column length. As the cylindrical block 2 moves downward, molten metal is continually added into the vessel 5 to maintain the liquid level of the molten metal at the top of the side wall 4. Typically, a heat source is used near the top of the vessel 5 to provide additional heat in this area for maintaining the molten mass in the molten state and preventing premature solidification. The dovetail 3 locks the electrode to the cylindrical block 2, as the block 2 moves downward. Through this process, for example, an electrode of approximately 15,000-25,000 pounds may be produced. The electrode is then laterally removed from the dovetail 3 and released from the cylindrical block for further processing.
As the cylindrical block 2 moves downward, however, streaks of molten metal may run down along the surface of the electrode and form icicle-like formations or "rundowns" over the sides of the dovetail 3. These "rundowns" can act as a latch that prevents removal of the electrode from the cylindrical block 2. Accordingly, these "rundowns" must be chiseled from the dovetail 3 so that the electrode can be withdrawn from the block 2.
Furthermore, such process generally provides a cast electrode that has a relatively uneven surface that is not well suited for uniform adhesion to other flat surfaces, such as a conducting solid cylinder which is used to introduce current into the electrode during the re-melting process. Thus, during subsequent vacuum arc or electroslag re-melting, introduction of current into or through the cast surface on many occasions causes arcing that results in damage to the re-melting equipment. A massive plunge/stub must be welded to one end of the electrode. The plunge/stub has a smooth surface and is used both to support the electrode weight and to introduce current into it. FIG. 4 illustrates the conventional electrode assembly wherein an electrode 6 is welded to the solid conducting stub 7 for subsequent re-melting of the electrode through the application of a current thereto through the conducting stub 7.
The need to mechanically remove the "rundowns" from the cylindrical block and the additional welding processes add a significant amount of time and cost to the continuous casting process. Accordingly, a continuous casting locking mechanism and electrode assembly is needed that eliminates these additional process steps to increase manufacturing time and efficiency.